1. Field of the Invention
The invention relates to novel bleach activators, bleaching compositions containing these activators, and a method for bleaching laundry fabrics.
2. The Prior Art
Active oxygen-releasing compounds are well known as effective bleaching agents. These compounds are frequently incorporated into detergent compositions for stain and soil removal. Unlike the traditional sodium hypochlorite, hydrogen peroxide-releasing compounds are less aggressive and thus more compatible with the ingredients of detergent compositions. On the other hand, the bleaching activity of these compounds is highly temperature dependent. Use of hydrogen peroxide releasing bleaches is only practical where the wash temperatures are above 60.degree. C. Below this temperature, extremely high amounts of the active oxygen-releasing compound must be added to achieve the desired result. Frequently, wash temperatures are, however, on the low side for various reasons including that of energy efficiency.
The temperature problem can be solved by use of transition metal containing compounds which catalyze or activate the oxygen-releasing material. Typical metals known in the art include those of iron, cobalt, manganese and copper. Only select transition metal substances provide the efficient catalysis necessary for laundry fabrics application. Furthermore, not all types of stains are removable by the transition metal-hydrogen peroxide generated substances. Especially difficult to bleach are hydrophobic stains such as those caused by spaghetti sauce and the like.
As one approach to an improved bleach activator, attention has been focused upon the chemistry of copper (II) polyamine complexes. Certain of these complexes have been reported as binding peroxide. For instance, see Thompson, J. Am. Chem. Soc. 106, 8309 (1984) and Thompson, Biological and Inorganic Copper Chemistry, Vol. 2, Karlin and Zubieta, Editors, Adenine Press (1986). Tetraethylethylenediamine ligands have been shown by Thompson to stabilize the formation of .mu.-peroxodicopper (II) complexes using dioxygen and Cu(I) compounds. Basolo and Murmann, J. Am. Chem. Soc. 74, 5243 (1952) and 76 211 (1954) report the chelating tendencies and hydrolytic stability of copper (II) dibromide complexes of various ethylene diamine ligands. Among those ligands are N,N'-dimethyl, -diethyl, -dipropyl, and -dibutyl analogs. None of the aforementioned references suggest, however, that these copper complexes can be employed to promote hydrogen peroxide activation using active oxygen-releasing compounds such as sodium perborate in the laundering of fabrics.
Accordingly, it is an object of the present invention to provide novel bleach activators that together with active oxygen-releasing compounds are capable of yielding peroxides over a wide temperature range including that of under 60.degree. C.
Another object of the present invention is to provide novel bleach activators that are highly efficient in removing hydrophobic stains.
A further object of the present invention is to provide a bleaching composition that is highly effective at cleaning soiled fabrics.